Alcoholic fermented beverages, for example beers, have a tendency to produce haze during storage and a number of products and processes are known for the removal of haze, and haze forming constituents. Filtration can remove the initial haze or turbidity from the beer, but in certain cases a further haze can develop on storage, particularly if the beer is stored at temperatures near 0.degree. C. This so-called chill-haze would only be noticeable at the point of consumption and consequently could not be removed.
It is therefore desirable to remove during production of the alcoholic beverage both the haze developed during the fermentation processes or on standing prior to final processing together with the haze precursors which may develop haze during storage.
The materials used for treating the beverage must not remove the components which are essential to the character, i.e. body and flavour, of the beer or the head forming components and colouring.
Various materials such as bentonites, active carbon, polyvinylpyrollidone and silicas have been previously proposed for this purpose and are used commercially, but silicas are preferred because they are selective in removing the protein species responsible for haze formation without impairing the desired properties of the beverage.
Prior literature shows that silicas either in the form of xerogels, hydrogels and precipitated silicas with surface areas ranging from 200 to 1000m.sup.2 g.sup.-1, pore volumes 0.35 to 2.5 ccg.sup.-1 and particle sizes in the range 3 to 30 .mu. can be used to remove protein from beer. More specifically the use of silica hydrogels with surface areas greater than 700 m.sup.2 g.sup.-1 are disclosed in GB 1, 215, 928 for the treatment of beer, and reference is also made that the hydrogel can be used as a slurry although the powder form is preferred. The specification contains no information on the preparation of a slurry.
Fine particle sized xerogels and precipitated silicas have one pronounced disadvantage and that is their excessive dusting when introduced into the dosing equipment normally employed in the brewery. Silica hydrogels containing 30% to 60% by weight of SiO.sub.2 are practically non-dusting, but these materials are extremely cohesive and as a consequence they require specially designed equipment for them to be successfully handled in bulk.
In the brewing process, filter room materials used to aid filtration and induce stabilisation are dosed to the beer either in aqueous suspension or dispersed in beer. It would be desirable, therefore, to provide a stable pumpable suspension of fine particle sized synthetic silica for use in the brewing, eliminating the need for secondary processing, with it associated problems. A stable pumpable suspension of fine particle sized silica hydrogel is preferred in view of its improved filtration performance over finely ground xerogels and precipitated silicas. The suspension of fine particle size amorphous silicas would need to remain pumpable on storage and be free of micro-organisms, such as yeasts and moulds, at the point of use.
Although the present invention is directed to the treatment of beers, which term includes ales, lagers and stouts, it is applicable to other fermented liquids eg. wines, which are liable to generate haze on storage.